Flutter BLoC生成新状态后未更新BlocBuilder()
我对flutter上的BLoC模式还不熟悉,我正试图用它重建一个混乱的flutter应用程序。目前,我打算获取用户应用程序的列表,并使用ListView.builder()显示它们。问题是,每当AppsBloc的状态发生变化时,我的无状态小部件都不会更新以显示新状态。我试过:Flutter BLoC生成新状态后未更新BlocBuilder(),flutter,dart,bloc,Flutter,Dart,Bloc,我对flutter上的BLoC模式还不熟悉,我正试图用它重建一个混乱的flutter应用程序。目前,我打算获取用户应用程序的列表,并使用ListView.builder()显示它们。问题是,每当AppsBloc的状态发生变化时,我的无状态小部件都不会更新以显示新状态。我试过: 使用main.dart中的MultiBlocProvider(),而不是将此appsBloc嵌套在包含整个应用程序的themeBloc中 返回列表而不是映射,即使我的aux方法返回正确的映射 使用StatefulWidg
- 使用main.dart中的MultiBlocProvider(),而不是将此appsBloc嵌套在包含整个应用程序的themeBloc中
- 返回列表而不是映射,即使我的aux方法返回正确的映射
- 使用StatefulWidget,仅在ListView上使用BlocProvider()
import 'dart:async';
import 'package:bloc/bloc.dart';
import 'package:device_apps/device_apps.dart';
import 'package:equatable/equatable.dart';
part 'apps_event.dart';
part 'apps_state.dart';
class AppsBloc extends Bloc<AppsEvent, AppsState> {
@override
AppsState get initialState => AppsInitial();
@override
Stream<AppsState> mapEventToState(AppsEvent event) async* {
yield AppsLoadInProgress();
if (event is AppsLoadRequest) {
yield* _mapAppsLoadSuccessToState();
}
}
Stream<AppsState> _mapAppsLoadSuccessToState() async* {
try {
final allApps = await DeviceApps.getInstalledApplications(
onlyAppsWithLaunchIntent: true, includeSystemApps: true);
final listaApps = allApps
..sort((a, b) =>
a.appName.toLowerCase().compareTo(b.appName.toLowerCase()));
final Map<Application, bool> res =
Map.fromIterable(listaApps, value: (e) => false);
yield AppsLoadSuccess(res);
} catch (_) {
yield AppsLoadFailure();
}
}
}
导入'dart:async';
导入“包:bloc/bloc.dart”;
导入“包:设备应用程序/设备应用程序.dart”;
导入“包:equalable/equalable.dart”;
“应用程序和事件.dart”部分;
“应用程序州.省道”部分;
类AppsBloc扩展了Bloc{
@凌驾
AppsState get initialState=>AppsInitial();
@凌驾
流mapEventToState(AppsEvent事件)异步*{
收益率AppsLoadInProgress();
if(事件为AppsLocadRequest){
yield*_mappsLoadSuccessToState();
}
}
流\u mapAppsLoadSuccessToState()异步*{
试一试{
最终allApps=等待设备Apps.GetInstalledApplication(
仅适用于具有启动意图的应用程序:true,包括系统应用程序:true);
最终列表aapps=allApps
…排序((a,b)=>
a、 appName.toLowerCase().compareTo(b.appName.toLowerCase());
最终地图资源=
Map.fromIterable(listaApps,值:(e)=>false);
收益率AppsLoadSuccess(res);
}接住{
屈服于AppsLoadFailure();
}
}
}
apps\u event.dart
part of 'apps_bloc.dart';
abstract class AppsEvent extends Equatable {
const AppsEvent();
@override
List<Object> get props => [];
}
class AppsLoadRequest extends AppsEvent {}
apps_bloc.dart'的一部分;
抽象类AppsEvent扩展了equalable{
常数AppsEvent();
@凌驾
列表获取道具=>[];
}
类AppsLocadRequest扩展AppsEvent{}
应用程序_state.dart
part of 'apps_bloc.dart';
abstract class AppsState extends Equatable {
const AppsState();
@override
List<Object> get props => [];
}
class AppsInitial extends AppsState {
@override
String toString() => "State: AppInitial";
}
class AppsLoadInProgress extends AppsState {
@override
String toString() => "State: AppLoadInProgress";
}
class AppsLoadSuccess extends AppsState {
final Map<Application, bool> allApps;
const AppsLoadSuccess(this.allApps);
@override
List<Object> get props => [allApps];
@override
String toString() => "State: AppLoadSuccess, ${allApps.length} entries";
}
class AppsLoadFailure extends AppsState {
@override
String toString() => "State: AppLoadFailure";
}
apps_bloc.dart'的一部分;
抽象类AppsState扩展了Equalable{
常量AppsState();
@凌驾
列表获取道具=>[];
}
类appsintial扩展了AppsState{
@凌驾
字符串toString()=>“状态:AppInitial”;
}
类AppsLoadInProgress扩展了AppsState{
@凌驾
字符串toString()=>“状态:AppLoadInProgress”;
}
类AppsLocadSuccess扩展了AppsState{
阿拉普斯最终地图;
const appsloadsucces(this.allApps);
@凌驾
列表获取道具=>[allApps];
@凌驾
String toString()=>“状态:AppLoadSuccess,${allApps.length}个条目”;
}
类AppsLoadFailure扩展了AppsState{
@凌驾
字符串toString()=>“状态:AppLoadFailure”;
}
主屏幕省道
class MainScreen extends StatelessWidget {
const MainScreen({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return TabBarView(
children: <Widget>[
HomeScreen(),
BlocProvider(
create: (BuildContext context) => AppsBloc(),
child: AppsScreen(),
)
,
],
);
}
}
class AppsScreen extends StatelessWidget {
const AppsScreen({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
margin: EdgeInsets.fromLTRB(30, 5, 10, 0),
child: Column(children: <Widget>[
Row(
children: <Widget>[
Text("Apps"),
],
),
Row(children: <Widget>[
Container(
width: MediaQuery.of(context).size.width - 50,
height: MediaQuery.of(context).size.height - 150,
child: BlocBuilder<AppsBloc, AppsState>(
builder: (BuildContext context, AppsState state) {
if (state is AppsLoadSuccess)
return Text("LOADED");
else if (state is AppsInitial)
return GestureDetector(
onTap: () => AppsBloc().add(AppsLoadRequest()),
child: Text("INITIAL"));
else if (state is AppsLoadInProgress)
return Text("LOADING...");
else if (state is AppsLoadFailure)
return Text("LOADING FAILED");
},
),
),
])
])),
);
}
}
class主屏幕扩展了无状态小部件{
常量主屏幕({Key}):超级(Key:Key);
@凌驾
小部件构建(构建上下文){
返回选项卡视图(
儿童:[
主屏幕(),
BlocProvider(
create:(BuildContext context)=>AppsBloc(),
子项:AppsScreen(),
)
,
],
);
}
}
apps\u screen.dart
class MainScreen extends StatelessWidget {
const MainScreen({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return TabBarView(
children: <Widget>[
HomeScreen(),
BlocProvider(
create: (BuildContext context) => AppsBloc(),
child: AppsScreen(),
)
,
],
);
}
}
class AppsScreen extends StatelessWidget {
const AppsScreen({Key key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
margin: EdgeInsets.fromLTRB(30, 5, 10, 0),
child: Column(children: <Widget>[
Row(
children: <Widget>[
Text("Apps"),
],
),
Row(children: <Widget>[
Container(
width: MediaQuery.of(context).size.width - 50,
height: MediaQuery.of(context).size.height - 150,
child: BlocBuilder<AppsBloc, AppsState>(
builder: (BuildContext context, AppsState state) {
if (state is AppsLoadSuccess)
return Text("LOADED");
else if (state is AppsInitial)
return GestureDetector(
onTap: () => AppsBloc().add(AppsLoadRequest()),
child: Text("INITIAL"));
else if (state is AppsLoadInProgress)
return Text("LOADING...");
else if (state is AppsLoadFailure)
return Text("LOADING FAILED");
},
),
),
])
])),
);
}
}
class AppsScreen扩展了无状态小部件{
const-AppsScreen({Key}):super(Key:Key);
@凌驾
小部件构建(构建上下文){
返回脚手架(
主体:容器(
边距:LTRB(30,5,10,0)的边距,
子项:列(子项:[
划船(
儿童:[
文本(“应用程序”),
],
),
世界其他地区(儿童:[
容器(
宽度:MediaQuery.of(context).size.width-50,
高度:MediaQuery.of(context).size.height-150,
孩子:BlocBuilder(
生成器:(BuildContext上下文,AppsState状态){
if(状态为AppsLodSuccess)
返回文本(“已加载”);
else if(状态为应用)
返回手势检测器(
onTap:()=>AppsBloc().add(AppsLoadRequest()),
子项:文本(“首字母”);
else if(状态为AppsLoadInProgress)
返回文本(“加载…”);
else if(状态为AppsLoadFailure)
返回文本(“加载失败”);
},
),
),
])
])),
);
}
}
在GestureDetector.onTap()中创建一个新的AppsBloc()
,这是错误的。因此,您需要:
应用程序\u屏幕。省道:
AppsBloc _appsBloc;
@override
void initState() {
super.initState();
_appsBloc = BlocProvider.of<AppsBloc>(context);
}
//...
@override
Widget build(BuildContext context) {
//...
return GestureDetector(
onTap: () => _appsBloc.add(AppsLoadRequest()),
child: Text("INITIAL")
);
//...
}
在GestureDetector.onTap()
中创建一个新的AppsBloc()
,这是错误的。因此,您需要:
应用程序\u屏幕。省道:
AppsBloc _appsBloc;
@override
void initState() {
super.initState();
_appsBloc = BlocProvider.of<AppsBloc>(context);
}
//...
@override
Widget build(BuildContext context) {
//...
return GestureDetector(
onTap: () => _appsBloc.add(AppsLoadRequest()),
child: Text("INITIAL")
);
//...
}
这解决了我的问题,非常感谢!我以前也试过,但看起来我错过了一些重要的东西,现在它起作用了。干杯。这解决了我的问题,非常感谢!我以前也试过,但看起来我错过了一些重要的东西,现在它起作用了。干杯